MM-10417 Add local image proxy and enable by default (#9967)

* MM-10417 Add local image proxy and enable by default

* Remove unused function

* Add dependencies for willnorris/imageproxy

* Fixed compilation errors

* Lock to the master version of willnorris/imageproxy

* Fix atmos/camo proxy when no SiteURL is specified

* Re-add default values for deprecated settings

* Fix unit tests added by merge

* Pass imageproxy to App struct

* Remove unneeded locking when creating the image proxy

* Remove empty test file

services/imageproxy/local.go

@@ -0,0 +1,99 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package imageproxy
+
+import (
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+
+	"github.com/mattermost/mattermost-server/mlog"
+	"github.com/mattermost/mattermost-server/services/httpservice"
+	"willnorris.com/go/imageproxy"
+)
+
+var imageContentTypes = []string{
+	"image/bmp", "image/cgm", "image/g3fax", "image/gif", "image/ief", "image/jp2",
+	"image/jpeg", "image/jpg", "image/pict", "image/png", "image/prs.btif", "image/svg+xml",
+	"image/tiff", "image/vnd.adobe.photoshop", "image/vnd.djvu", "image/vnd.dwg",
+	"image/vnd.dxf", "image/vnd.fastbidsheet", "image/vnd.fpx", "image/vnd.fst",
+	"image/vnd.fujixerox.edmics-mmr", "image/vnd.fujixerox.edmics-rlc",
+	"image/vnd.microsoft.icon", "image/vnd.ms-modi", "image/vnd.net-fpx", "image/vnd.wap.wbmp",
+	"image/vnd.xiff", "image/webp", "image/x-cmu-raster", "image/x-cmx", "image/x-icon",
+	"image/x-macpaint", "image/x-pcx", "image/x-pict", "image/x-portable-anymap",
+	"image/x-portable-bitmap", "image/x-portable-graymap", "image/x-portable-pixmap",
+	"image/x-quicktime", "image/x-rgb", "image/x-xbitmap", "image/x-xpixmap", "image/x-xwindowdump",
+}
+
+type LocalBackend struct {
+	proxy *ImageProxy
+
+	// The underlying image proxy implementation provided by the third party library
+	impl *imageproxy.Proxy
+}
+
+func makeLocalBackend(proxy *ImageProxy) *LocalBackend {
+	impl := imageproxy.NewProxy(proxy.HTTPService.MakeTransport(false), nil)
+
+	baseURL, err := url.Parse(*proxy.ConfigService.Config().ServiceSettings.SiteURL)
+	if err != nil {
+		mlog.Error("Failed to set base URL for image proxy. Relative image links may not work.", mlog.Err(err))
+	} else {
+		impl.DefaultBaseURL = baseURL
+	}
+
+	impl.Timeout = time.Duration(httpservice.RequestTimeout)
+	impl.ContentTypes = imageContentTypes
+
+	return &LocalBackend{
+		proxy: proxy,
+		impl:  impl,
+	}
+}
+
+func (backend *LocalBackend) GetImage(w http.ResponseWriter, r *http.Request, imageURL string) {
+	// The interface to the proxy only exposes a ServeHTTP method, so fake a request to it
+	req, err := http.NewRequest(http.MethodGet, "/"+imageURL, nil)
+	if err != nil {
+		// http.NewRequest should only return an error on an invalid URL
+		mlog.Error("Failed to create request for proxied image", mlog.String("url", imageURL), mlog.Err(err))
+
+		w.WriteHeader(http.StatusBadRequest)
+		w.Write([]byte{})
+		return
+	}
+
+	backend.impl.ServeHTTP(w, req)
+}
+
+func (backend *LocalBackend) GetProxiedImageURL(imageURL string) string {
+	siteURL := *backend.proxy.ConfigService.Config().ServiceSettings.SiteURL
+
+	if imageURL == "" || imageURL[0] == '/' || strings.HasPrefix(imageURL, siteURL) {
+		return imageURL
+	}
+
+	return siteURL + "/api/v4/image?url=" + url.QueryEscape(imageURL)
+}
+
+func (backend *LocalBackend) GetUnproxiedImageURL(proxiedURL string) string {
+	siteURL := *backend.proxy.ConfigService.Config().ServiceSettings.SiteURL
+
+	if !strings.HasPrefix(proxiedURL, siteURL+"/api/v4/image?url=") {
+		return proxiedURL
+	}
+
+	parsed, err := url.Parse(proxiedURL)
+	if err != nil {
+		return proxiedURL
+	}
+
+	u := parsed.Query()["url"]
+	if len(u) == 0 {
+		return proxiedURL
+	}
+
+	return u[0]
+}